1. Technical Field
The present invention relates to a conductive pattern formation ink, a conductive pattern and a wiring substrate, and more specifically relates to a conductive pattern formation ink, a conductive pattern formed by the conductive pattern formation ink and a wiring substrate provided with the conductive pattern.
2. Related Art
A ceramic circuit substrate including a substrate (a ceramic substrate) formed of a ceramic material and a wiring formed of a metal material and provided on the substrate has been widely used as a circuit substrate (a wiring substrate) on which electronic parts are to be mounted.
In such a ceramic circuit substrate, the substrate (the ceramic substrate) itself is formed of a multifunctional material such as the ceramic material. Therefore, there are merits in that if a multilayer substrate is produced using a plurality of such substrates, inner layer parts can be formed easily between the substrates with high dimensional accuracy.
Such a ceramic circuit substrate can be produced by supplying a composition containing metal particles on a ceramic molded body made of a material containing ceramic particles and a binder in a predetermined pattern corresponding to a pattern of wirings (a conductive pattern) to be formed, and then subjecting the ceramic molded body on which the composition is supplied to a degreasing and sintering treatment.
A screen printing method has been widely used as a method of forming a pattern on the ceramic molded body. On the other hand, recently, miniaturization of the wirings and reduction of pitches between the wirings are required for densification of the ceramic circuit substrate.
However, use of the screen printing method has disadvantage for the miniaturization of the wirings (e.g., formation of wirings each having a line width of about 60 μm or less) and the reduction of the pitches between the wirings. As a result, it is difficult to respond to the above requirement.
For this reason, recently, as an alternative method of forming the pattern on the ceramic molded body, there has been proposed use of what is called an ink jet method, i.e., a liquid droplet ejecting method by which a liquid material (a conductive pattern formation ink) containing metal particles is ejected in the form of liquid droplets from a liquid droplet ejection head, (see, e.g., JP-A-2007-84387).
Meanwhile, an industrial liquid droplet ejection apparatus to be used for forming the conductive pattern is clearly different from a consumer liquid droplet ejection apparatus to be used in a printer. For example, in order to produce a large quantity of products, the industrial liquid droplet ejection apparatus must be able to eject the great number of liquid droplets continuously for a long period of time.
Further, in general, fluid cut of an industrial ink to be used for forming the conductive pattern when ejecting it is worse than that of a consumer ink to be used in the printer. As a result, the industrial ink is apt to remain in ejection portions (nozzles) of the liquid droplet ejection head.
Furthermore, clogging of the ejection portions of the liquid droplet ejection head is likely to occur due to aggregation of solid contents such as the metal particles contained in the industrial ink. This frequently causes changes of ejecting directions of the liquid droplets. Such unstability of an ejecting property of the liquid droplets makes it impossible to form a fine conductive pattern using the industrial ink.